Friction loss reduction in viscoelastic surfactant fracturing fluids using low molecular weight water-soluble polymers

Abstract

Adding relatively low molecular weight water-soluble friction loss reduction polymers to an aqueous fluid gelled with a viscoelastic surfactant (VES) increases the critical generalized Reynold's number at which the Fanning friction factor increases and friction pressure starts to increase rapidly. The water-soluble polymeric friction loss reduction additives lower surface pumping pressure in VES-gelled fracturing fluids for a given pump rate, thus lowering hydraulic horsepower (HHP) requirements for pumping fluids downhole, e.g. for hydraulic fracturing or frac packing treatments of subterranean formations.

1. An aqueous viscoelastic treating fluid comprising:
 an aqueous brine base fluid gelled by from about 0.2 to about 12.0 vol % of the total aqueous viscoelastic treating fluid of a viscoelastic surfactant (VES) gelling agent; and 
 a water-soluble, polymeric friction loss reduction agent having a molecular weight of 250,000 or lower, and which is selected from the group consisting of karaya, locust bean, pectin, tragacanth, acacia, agar, scleroglucan; and polymers and copolymers selected from the group consisting of acetamide, and formamide. 
 
     
     
       2. The fluid of  claim 1  where the amount of water-soluble, polymeric friction loss reduction agent is effective to improve the flow of the aqueous viscoelastic treating fluid as compared with an identical fluid absent the agent when the fluid is flowed at or above a critical generalized Reynold's number at which friction pressure would rapidly increase, but for the presence of the friction loss reduction agent. 
     
     
       3. The fluid of  claim 1  where the friction loss reduction agent has a molecular weight of 125,000 or lower. 
     
     
       4. An aqueous viscoelastic treating fluid comprising:
 a brine base fluid gelled by from about 0.2 to about 12.0 vol % of the total aqueous viscoelastic treating fluid of a viscoelastic surfactant (VES) gelling agent; and 
 from about 2 to about 40 pptg (about 0.2 to about 4.8 kg/m 3 ) of a water-soluble, polymeric friction loss reduction agent where the friction loss reduction agent has a molecular weight of 250,000 or lower and is selected from the group consisting of karaya, locust bean, pectin, tragacanth, acacia, agar, scleroglucan; and polymers and copolymers selected from the group consisting of acetamide, and formamide. 
 
     
     
       5. An aqueous viscoelastic treating fluid comprising:
 a brine base fluid gelled by from about 0.2 to about 12.0 vol % of the total aqueous viscoelastic treating fluid of a viscoelastic surfactant (VES) gelling agent; and 
 from about 2 to about 40 pptg (about 0.2 to about 4.8 kg/m 3 ) of a water-soluble, polymeric friction loss reduction agent where the friction loss reduction agent has a molecular weight of 125,000 or lower and is selected from the group consisting of karaya, locust bean, pectin, tragacanth, acacia, agar, scleroglucan; and polymers and copolymers selected from the group consisting of acetamide, and formamide.